JP4593099B2 - Liquid crystal epitaxial growth method of single crystal silicon carbide and heat treatment apparatus used therefor - Google Patents
Liquid crystal epitaxial growth method of single crystal silicon carbide and heat treatment apparatus used therefor Download PDFInfo
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本発明は、単結晶炭化ケイ素の液相エピタキシャル成長法及びそれに用いられる熱処理装置に関するものである。 The present invention relates to a liquid phase epitaxial growth method of single crystal silicon carbide and a heat treatment apparatus used therefor.
炭化ケイ素（以下、ＳｉＣという。）は、耐熱性及び機械的強度に優れているだけでなく、放射線にも強く、さらに不純物の添加によって電子や正孔の価電子制御が容易である上、広い禁制帯幅を持つ（因みに、６Ｈ型のＳｉＣ単結晶で約３．０ｅＶ、４Ｈ型のＳｉＣ単結晶で３．３ｅＶ）ために、シリコン（以下、Ｓｉという。）やガリウムヒ素（以下、ＧａＡｓという。）などの既存の半導体材料では実現することができない高温、高周波、耐電圧・耐環境性を実現することが可能で、次世代のパワーデバイス、高周波デバイス用半導体材料として注目され、かつ期待されている。また、六方晶ＳｉＣは、窒化ガリウム（以下、ＧａＮという。）と格子定数が近く、ＧａＮの基板として期待されている。 Silicon carbide (hereinafter referred to as SiC) is not only excellent in heat resistance and mechanical strength, but is also resistant to radiation, and it is easy to control the valence electrons of electrons and holes by addition of impurities. Since it has a forbidden band width (by the way, it is about 3.0 eV for a 6H type SiC single crystal and 3.3 eV for a 4H type SiC single crystal), silicon (hereinafter referred to as Si) or gallium arsenide (hereinafter referred to as GaAs). It is possible to realize high temperature, high frequency, withstand voltage / environment resistance that cannot be realized with existing semiconductor materials such as.), And has attracted attention and is expected as a semiconductor material for next generation power devices and high frequency devices. ing. Hexagonal SiC has a lattice constant close to that of gallium nitride (hereinafter referred to as GaN), and is expected as a GaN substrate.
この種の単結晶ＳｉＣは、例えば、特許文献１に記載されているように、ルツボ内の低温側に種結晶を固定配置し、高温側に原料となるＳｉを含む粉末を配置してルツボを不活性雰囲気中で１４５０〜２４００℃の高温に加熱することによって、Ｓｉを含む粉末を昇華させて低温側の種結晶の表面上で再結晶させて単結晶の育成を行なう昇華再結晶法（改良レーリー法）によって形成されているものがある。 For example, as described in Patent Document 1, this type of single-crystal SiC has a seed crystal fixedly disposed on the low temperature side of the crucible, and a powder containing Si as a raw material is disposed on the high temperature side, and the crucible is A sublimation recrystallization method (improvement) in which a single crystal is grown by sublimating a powder containing Si by heating to a high temperature of 1450 to 2400 ° C. in an inert atmosphere and recrystallizing on the surface of the seed crystal on the low temperature side. Some are formed by the Rayleigh method.
また、例えば、特許文献２に記載されているように、ＳｉＣ単結晶基板とＳｉ原子及びＣ原子により構成された板材とを微小隙間を隔てて互いに平行に対峙させた状態で大気圧以下の不活性ガス雰囲気、且つ、ＳｉＣ飽和蒸気雰囲気下でＳｉＣ単結晶基板側が板材よりも低温となるように温度傾斜を持たせて熱処理することにより、微小隙間内でＳｉ原子及びＣ原子を昇華再結晶させてＳｉＣ単結晶基板上に単結晶を析出させるものもある。 Further, for example, as described in Patent Document 2, a SiC single crystal substrate and a plate material composed of Si atoms and C atoms are opposed to each other in a state where they are opposed to each other in parallel with a minute gap therebetween. Si atoms and C atoms are sublimated and recrystallized in minute gaps by heat treatment in an active gas atmosphere and a SiC saturated vapor atmosphere with a temperature gradient so that the SiC single crystal substrate side is at a lower temperature than the plate material. In some cases, a single crystal is deposited on a SiC single crystal substrate.
また、例えば、特許文献３に記載されているように、液相エピタキシャル成長法によってＳｉＣ単結晶上に第１のエピタキシャル層を形成した後に、ＣＶＤ法によって表面に第２のエピタキシャル層を形成して、マイクロパイプ欠陥を除去するものもある。 For example, as described in Patent Document 3, after forming the first epitaxial layer on the SiC single crystal by the liquid phase epitaxial growth method, the second epitaxial layer is formed on the surface by the CVD method, Some remove micropipe defects.
しかしながら、これら単結晶ＳｉＣの形成方法のうち、例えば、特許文献１や特許文献２に記載の昇華再結晶法の場合は、成長速度が数１００μｍ／ｈｒと非常に早い反面、昇華の際にＳｉＣ粉末がいったんＳｉ、ＳｉＣ２、Ｓｉ２Ｃに分解されて気化し、さらにルツボの一部と反応する。このために、温度変化によって種結晶の表面に到達するガスの種類が異なり、これらの分圧を化学量論的に正確に制御することが技術的に非常に困難である。また、不純物も混入しやすく、その混入した不純物や熱に起因する歪みの影響で結晶欠陥やマイクロパイプ欠陥等を発生しやすく、また、多くの核生成に起因する結晶粒界の発生など、性能的、品質的に安定した単結晶ＳｉＣが得られないという問題がある。 However, among the methods for forming single crystal SiC, for example, in the case of the sublimation recrystallization method described in Patent Document 1 or Patent Document 2, the growth rate is very fast, such as several hundred μm / hr. The powder is once decomposed and vaporized into Si, SiC 2 and Si 2 C, and further reacts with a part of the crucible. For this reason, the types of gases that reach the surface of the seed crystal differ depending on the temperature change, and it is technically very difficult to control these partial pressures stoichiometrically accurately. Impurities are also likely to be mixed in, and crystal defects and micropipe defects are likely to occur due to the influence of the mixed impurities and strain caused by heat. In addition, performance such as generation of crystal grain boundaries due to many nucleation There is a problem that single crystal SiC stable in quality and quality cannot be obtained.
一方、特許文献３に記載のＬＰＥ法の場合は、昇華再結晶法で見られるようなマイクロパイプ欠陥や結晶欠陥などの発生が少なく、昇華再結晶法で製造されるものに比べて品質的に優れた単結晶ＳｉＣが得られる。その反面、成長過程が、Ｓｉ融液中へのＣの溶解度によって律速されるために、成長速度が１０μｍ／ｈｒ以下と非常に遅くて単結晶ＳｉＣの生産性が低く、製造装置内の液相を精密に温度制御しなくてはならない。また、工程が複雑となり、単結晶ＳｉＣの製造コストが非常に高価なものになる。 On the other hand, in the case of the LPE method described in Patent Document 3, the occurrence of micropipe defects and crystal defects as seen in the sublimation recrystallization method is small, and the quality is higher than that produced by the sublimation recrystallization method. Excellent single crystal SiC is obtained. On the other hand, since the growth process is rate-determined by the solubility of C in the Si melt, the growth rate is very slow, 10 μm / hr or less, and the productivity of single crystal SiC is low. The temperature must be precisely controlled. Further, the process becomes complicated, and the manufacturing cost of single crystal SiC becomes very expensive.
本発明は前記問題に鑑みてなされたもので、マイクロパイプ欠陥や界面欠陥等の発生が少ないとともに、幅広なテラスを有し表面の平坦度の高い、高品質、高性能な単結晶ＳｉＣの液相エピタキシャル成長法及びそれに用いられる熱処理装置を提供することを目的とする。 The present invention has been made in view of the above problems, and has a high quality, high performance single crystal SiC liquid that has a wide terrace and a high surface flatness while generating few micropipe defects and interface defects. An object is to provide a phase epitaxial growth method and a heat treatment apparatus used therefor.
前記課題を解決するための本発明に係る単結晶ＳｉＣの液相エピタキシャル成長法は、種結晶となる単結晶炭化ケイ素基板と多結晶炭化ケイ素基板とを重ね、密閉容器内に設置して、高温熱処理を行なうことによって、前記単結晶炭化ケイ素基板と前記多結晶炭化ケイ素基板との間に、熱処理中に極薄金属シリコン融液を介在させ、前記単結晶炭化ケイ素基板上に単結晶炭化ケイ素を液相エピタキシャル成長させる単結晶炭化ケイ素の液相エピタキシャル成長法であって、前記単結晶炭化ケイ素基板と多結晶炭化ケイ素基板との間で温度差を設けずに、前記単結晶炭化ケイ素基板と多結晶炭化ケイ素基板とを１４００℃〜２３００℃に加熱して微結晶粒界の存在しない、表面のマイクロパイプ欠陥密度が１／ｃｍ2以下である単結晶炭化ケイ素を製造するものである。 The liquid crystal epitaxial growth method of single crystal SiC according to the present invention for solving the above-mentioned problem is a high temperature heat treatment in which a single crystal silicon carbide substrate to be a seed crystal and a polycrystalline silicon carbide substrate are stacked and placed in a sealed container. By performing an ultrathin metal silicon melt between the single crystal silicon carbide substrate and the polycrystalline silicon carbide substrate during the heat treatment, and the single crystal silicon carbide liquid is placed on the single crystal silicon carbide substrate. A liquid phase epitaxial growth method of single crystal silicon carbide for phase epitaxial growth, wherein the single crystal silicon carbide substrate and the polycrystalline silicon carbide are formed without providing a temperature difference between the single crystal silicon carbide substrate and the polycrystalline silicon carbide substrate. the substrate is heated to 1 400 ° C. to 2300 ° C. no fine grain boundaries, micropipe defect density of the surface is 1 / cm 2 or less single-crystal silicon carbide It is intended to produce a.
成長結晶内部に微結晶粒界が存在せず、表面のマイクロパイプ欠陥の密度が１／ｃｍ2以下の単結晶ＳｉＣとできるため、各種半導体デバイスとしての適用が可能となる。ここで、マイクロパイプ欠陥とは、ピンホールとも呼ばれ、結晶の成長方向に沿って存在する数μｍ以下の直径の管状の空隙のことである。また、使用する種結晶となる単結晶ＳｉＣ基板は、４Ｈ−ＳｉＣ、６Ｈ−ＳｉＣの全ての結晶面で可能であるが，好ましくは（０００１）Ｓｉ面を使用することが好ましい。また、多結晶ＳｉＣ基板には、平均粒子径が５μｍ〜１０μｍの粒子径で、粒子径が略均一なものが好ましい。このため、多結晶ＳｉＣの結晶構造には特に限定はなく、３Ｃ−ＳｉＣ、４Ｈ−ＳｉＣ、６Ｈ−ＳｉＣのいずれをも使用することができるが、好ましくは３Ｃ−ＳｉＣであることが好ましい。 Growth absent fine grain boundary crystal therein, the density of micropipe defects on the surface can be a 1 / cm 2 or less of the single crystal SiC, the application of the various semiconductor devices becomes possible. Here, the micropipe defect is also called a pinhole, and is a tubular void having a diameter of several μm or less that exists along the crystal growth direction. The single crystal SiC substrate used as a seed crystal can be formed on all crystal planes of 4H—SiC and 6H—SiC, but preferably a (0001) Si plane is used. The polycrystalline SiC substrate preferably has an average particle size of 5 μm to 10 μm and a substantially uniform particle size. For this reason, there is no particular limitation on the crystal structure of polycrystalline SiC, and any of 3C—SiC, 4H—SiC, and 6H—SiC can be used, but 3C—SiC is preferred.
また、本発明によると、熱処理時に単結晶ＳｉＣ基板と多結晶ＳｉＣ基板との間にＳｉが毛細管現象により界面のすみずみに濡れが浸透して極薄の金属Ｓｉ融液層を形成する。多結晶ＳｉＣ基板から流れ出したＣ原子はＳｉ融液層を通して単結晶ＳｉＣ基板に供給されて、その単結晶ＳｉＣ基板上に単結晶ＳｉＣとして液相エピタキシャル成長する。このため、成長初期から終了まで欠陥の誘発を抑制できる。また、従来のように、溶融Ｓｉ中に浸漬して処理する必要がないため、熱処理後に、種結晶となる単結晶ＳｉＣ基板及び多結晶ＳｉＣ基板に溶着するＳｉを除去する量が極めて少なくなる。また、単結晶ＳｉＣ基板と多結晶ＳｉＣ基板との間に、熱処理中に極薄金属Ｓｉ融液を介在させるため、単結晶ＳｉＣのエピタキシャル成長に必要な金属Ｓｉのみを単結晶ＳｉＣの液相エピタキシャル成長に使用できる。このため、熱処理時に薄いＳｉ層では外部との接触面積が最小となり、したがって不純物の進入確率が減り、高純度な単結晶ＳｉＣを形成することができる。 In addition, according to the present invention, during the heat treatment, Si permeates into every corner of the interface between the single crystal SiC substrate and the polycrystalline SiC substrate, thereby forming an extremely thin metal Si melt layer. The C atoms flowing out of the polycrystalline SiC substrate are supplied to the single crystal SiC substrate through the Si melt layer, and liquid phase epitaxially grows as single crystal SiC on the single crystal SiC substrate. For this reason, it is possible to suppress the induction of defects from the initial stage to the end of growth. In addition, since it is not necessary to immerse and process in molten Si as in the prior art, the amount of Si deposited on the single-crystal SiC substrate and polycrystalline SiC substrate that becomes the seed crystal after heat treatment is extremely reduced. Moreover, since an ultrathin metal Si melt is interposed between the single crystal SiC substrate and the polycrystalline SiC substrate during the heat treatment, only the metal Si necessary for the epitaxial growth of the single crystal SiC is used for the liquid phase epitaxial growth of the single crystal SiC. Can be used. For this reason, the contact area with the outside is minimized in the thin Si layer at the time of the heat treatment, so that the probability of entry of impurities is reduced, and high-purity single crystal SiC can be formed.
単結晶ＳｉＣ基板と多結晶ＳｉＣ基板との間に温度差が形成されないため、熱平衡状態で熱処理することが可能となり、また金属Ｓｉ融液が薄いため熱対流が抑制される。このため、成長初期から終了まで欠陥の誘発を抑制できる。さらに、熱処理時に核生成が抑制されるため、形成される単結晶ＳｉＣの微小結晶粒界の生成が抑制できる。結果として、マイクロパイプ欠陥密度を１／ｃｍ2以下の単結晶ＳｉＣを形成することができる。また、簡易な熱処理装置を用いることができるとともに、加熱時の厳密な温度制御が必要ないことから製造コストの大幅な低減化が可能となる。 Since no temperature difference is formed between the single crystal SiC substrate and the polycrystalline SiC substrate, heat treatment can be performed in a thermal equilibrium state, and thermal convection is suppressed because the metal Si melt is thin. For this reason, it is possible to suppress the induction of defects from the initial stage to the end of growth. Furthermore, since nucleation is suppressed during the heat treatment, generation of fine crystal grain boundaries of the formed single crystal SiC can be suppressed . As a result, it is possible to form a 1 / cm 2 or less of the single crystal SiC micropipe defect density. In addition, a simple heat treatment apparatus can be used, and since strict temperature control during heating is not necessary, the manufacturing cost can be greatly reduced.
また、本発明に係る単結晶ＳｉＣの液相エピタキシャル成長法は、前述の発明において、前記密閉容器が、タンタル又は炭化タンタルのいずれかで形成されているものである。 The single-phase SiC liquid phase epitaxial growth method according to the present invention is the above-described invention in which the sealed container is formed of either tantalum or tantalum carbide.
密閉容器がタンタル又は炭化タンタルで形成されているため、密閉容器のＳｉＣ化を抑制するとともに、加熱室内を確実に圧力１０-2Ｐａ以下とすることができる。 Since the sealed container is formed of tantalum or tantalum carbide, it is possible to suppress the formation of SiC in the sealed container and to reliably set the pressure in the heating chamber to 10 −2 Pa or less.
また、本発明に係る単結晶ＳｉＣの液相エピタキシャル成長法は、前述の発明において、前記密閉容器が上容器及び下容器で形成され、前記上容器及び前記下容器の嵌合部からシリコン蒸気が漏れ出す程度に前記密閉容器内の圧力が前記加熱室内の圧力よりも高くなるように制御し、前記密閉容器内に不純物が混入するのを抑制するものである。 Further, in the liquid crystal epitaxial growth method of single crystal SiC according to the present invention, in the above-described invention, the sealed container is formed of an upper container and a lower container, and silicon vapor leaks from a fitting portion of the upper container and the lower container. The pressure in the sealed container is controlled to be higher than the pressure in the heating chamber to the extent that it is discharged, and impurities are prevented from being mixed into the sealed container.
密閉容器をこのような構造とすることによって、密閉容器内への不純物の混入を抑制することができる。これによって、バッググランド５×１０15／ｃｍ3以下の純度とできる。 By adopting such a structure for the sealed container, it is possible to suppress contamination of impurities into the sealed container. Thereby, the purity of the bag ground can be 5 × 10 15 / cm 3 or less.
また、本発明に係る単結晶ＳｉＣの液相エピタキシャル成長法は、前述の発明において、前記単結晶ＳｉＣの表面が、３分子層を最小単位とした原子オーダーステップと、幅広のテラスと、を有し、前記テラスの幅が１０μｍ以上であるものである。 Further, the liquid crystal epitaxial growth method of single crystal SiC according to the present invention includes the atomic order step in which the surface of the single crystal SiC has a trimolecular layer as a minimum unit and a wide terrace. The terrace has a width of 10 μm or more.
テラス幅が１０μｍ以上であるため、成長表面は、単結晶ＳｉＣ形成後に、機械加工等による表面処理をする必要がない。このため、加工工程を経ずとも製品とすることが可能となる。 Since the terrace width is 10 μm or more, the growth surface does not need to be surface-treated by machining or the like after the single crystal SiC is formed. For this reason, it becomes possible to make a product without going through a processing step.
また、本発明に係る単結晶ＳｉＣの液相エピタキシャル成長法は、前述の発明において、前記表面が、（０００１）Ｓｉ面であるものである。 Moreover, the liquid phase epitaxial growth method of the single crystal SiC according to the present invention is such that, in the above-described invention, the surface is a (0001) Si plane.
表面の面方位が（０００１）Ｓｉ面であるため、他の結晶面と比較して、表面エネルギーが低く、従って成長中の核形成エネルギーが高くなり、核形成しにくい。以上の理由から、液相成長後テラス幅の広い単結晶ＳｉＣとできる。なお、表面の面方位は、（０００１）Ｓｉ面に限定されるものではなく、４Ｈ−ＳｉＣ、６Ｈ−ＳｉＣの全ての結晶面を使用することが可能である。 Since the plane orientation of the surface is the (0001) Si plane, the surface energy is lower than that of other crystal planes. Therefore, the nucleation energy during growth is increased and nucleation is difficult. For the above reasons, single crystal SiC having a wide terrace width after liquid phase growth can be obtained. Note that the plane orientation of the surface is not limited to the (0001) Si plane, and all crystal planes of 4H—SiC and 6H—SiC can be used.
また、本発明に係る単結晶ＳｉＣの液相エピタキシャル成長法は、前述の発明において、前記極薄金属Ｓｉ融液が、５０μｍ以下の厚みであるものである。 Moreover, the liquid crystal epitaxial growth method of single crystal SiC according to the present invention is the above-described invention, wherein the ultrathin metal Si melt has a thickness of 50 μm or less.
熱処理中に単結晶ＳｉＣ基板と多結晶ＳｉＣ基板との間に介在される極薄金属Ｓｉ融液が５０μｍ以下、好ましくは３０μｍ以下であるため、多結晶ＳｉＣ基板から溶解したＣが単結晶ＳｉＣ基板表面へ拡散により輸送され、単結晶ＳｉＣの成長が促進される。前記極薄金属シリコン融液が５０μｍ以上の厚みになると、金属シリコン融液が不安定になり、またＣの輸送が阻害され、本発明に係る単結晶ＳｉＣの育成に適さない。 Since the ultra-thin metal Si melt interposed between the single crystal SiC substrate and the polycrystalline SiC substrate during the heat treatment is 50 μm or less, preferably 30 μm or less, C dissolved from the polycrystalline SiC substrate is a single crystal SiC substrate. It is transported to the surface by diffusion, and the growth of single crystal SiC is promoted. When the ultrathin metal silicon melt has a thickness of 50 μm or more, the metal silicon melt becomes unstable and the transport of C is hindered, which is not suitable for growing single crystal SiC according to the present invention.
本発明によれば、従来の昇華法等の高温熱処理環境と同一環境で局所的な液相エピタキシャル成長を高温で行なうことができるため、種結晶に含まれるマイクロパイプ欠陥を引き継がず、マイクロパイプ欠陥の閉塞を行なうことができる。また、成長表面が常にＳｉ融液と接するため、Ｓｉ過剰の状態が形成され、Ｓｉの不足に起因する欠陥の発生が抑制されるとともに、使用しているＳｉ融液の外部との接触面積が微小なため、成長表面への不純物の混入が抑制でき、高純度で結晶性に優れた高品質高性能の単結晶ＳｉＣを育成することができる。しかも従来のＬＰＥ法に比べて、本成長法は非常に高温での成長が可能であるために、従来のＬＰＥ法に比べて成長速度を著しく速くすることができ、高品質単結晶ＳｉＣの育成効率を非常に高くすることができる。さらに、単結晶育成時に厳密な温度勾配制御をする必要性がなく、簡易な装置によることが可能となる。これらのことから、ＳｉやＧａＡｓなどの既存の半導体材科に比べて高温、高周波、耐電圧、耐環境性に優れパワーデバイス、高周波デバイス用半導体材科として期待されている単結晶ＳｉＣの実用化を促進することができる。 According to the present invention, since local liquid phase epitaxial growth can be performed at a high temperature in the same environment as a high temperature heat treatment environment such as a conventional sublimation method, the micropipe defects contained in the seed crystal are not inherited, and the micropipe defects are not inherited. Occlusion can be performed. In addition, since the growth surface is always in contact with the Si melt, an excessive Si state is formed, the generation of defects due to the lack of Si is suppressed, and the contact area with the outside of the Si melt being used is increased. Since it is minute, it is possible to suppress the mixing of impurities on the growth surface, and it is possible to grow a high-quality, high-performance single-crystal SiC having high purity and excellent crystallinity. In addition, compared with the conventional LPE method, this growth method can grow at a very high temperature. Therefore, the growth rate can be remarkably increased as compared with the conventional LPE method, and the growth of high-quality single crystal SiC can be achieved. The efficiency can be very high. Furthermore, there is no need to strictly control the temperature gradient during single crystal growth, and a simple apparatus can be used. Therefore, practical application of single crystal SiC, which is superior in high temperature, high frequency, withstand voltage, and environmental resistance compared to existing semiconductor materials such as Si and GaAs, is expected as a semiconductor material for power devices and high frequency devices. Can be promoted.
以下、図面を参照しつつ、本発明に係る単結晶ＳｉＣの液相成長法の一実施形態例について説明する。 Hereinafter, an embodiment of a liquid phase growth method for single crystal SiC according to the present invention will be described with reference to the drawings.
図１は、本発明に係る単結晶ＳｉＣの液相エピタキシャル成長法に用いられる熱処理炉の実施形態の一例を示す断面概略図である。図１において、熱処理炉１は、加熱室２と、予備加熱室３と、予備加熱室３から加熱室２に続く前室４とで構成されている。そして、単結晶ＳｉＣ及び種結晶ＳｉＣ等が収容されている密閉容器５が予備加熱室３から前室４、加熱室２へと順次移動することで、単結晶ＳｉＣを育成するように構成されている。 FIG. 1 is a schematic cross-sectional view showing an example of an embodiment of a heat treatment furnace used in the liquid phase epitaxial growth method of single crystal SiC according to the present invention. In FIG. 1, the heat treatment furnace 1 includes a heating chamber 2, a preheating chamber 3, and a front chamber 4 that extends from the preheating chamber 3 to the heating chamber 2. The sealed container 5 containing single crystal SiC, seed crystal SiC, and the like is configured to grow single crystal SiC by sequentially moving from the preheating chamber 3 to the front chamber 4 and the heating chamber 2. Yes.
図１に示すように、熱処理炉１は、加熱室２、予備加熱室３、前室４が連通している。このため、各室を予め所定の圧力下に制御することが可能となる。また、各室毎にゲートバルブ７等を設けることによって、各室毎に圧力調整をすることも可能である。これによって密閉容器５の移動時においても、外気に触れることなく、所定圧力下の炉内を図示しない移動手段によって移動させることができるため、不純物の混入等を抑制することができる。 As shown in FIG. 1, the heat treatment furnace 1 is connected to a heating chamber 2, a preheating chamber 3, and a front chamber 4. For this reason, it becomes possible to control each chamber under a predetermined pressure in advance. Further, it is possible to adjust the pressure for each chamber by providing a gate valve 7 or the like for each chamber. As a result, even when the sealed container 5 is moved, the inside of the furnace under a predetermined pressure can be moved by a moving means (not shown) without touching the outside air, so that contamination of impurities and the like can be suppressed.
予備加熱室３は、ランプ又はロッドヒータ等の加熱手段（本実施形態においては、ランプを用いている態様を示している。）６が設けられ、急速に８００〜１０００℃程度にまで加熱が可能な加熱炉になっている。また、予備加熱室３と前室４との接続部分には、ゲートバルブ７が設けらており、予備加熱室３及び前室４の圧力制御を容易なものとしている。密閉容器５は、この予備加熱室３で、テーブル８に載置された状態で８００℃以上に予め加熱された後、予備加熱室３と前室４との圧力調整が済み次第、前室４に設けられている昇降式のサセプタ９に設置するように移動させられる。 The preheating chamber 3 is provided with heating means 6 such as a lamp or a rod heater (in this embodiment, a mode using a lamp is shown) 6 and can be rapidly heated to about 800 to 1000 ° C. It is a simple heating furnace. In addition, a gate valve 7 is provided at a connection portion between the preheating chamber 3 and the front chamber 4 to facilitate pressure control of the preheating chamber 3 and the front chamber 4. The airtight container 5 is preheated to 800 ° C. or higher in the state of being placed on the table 8 in the preheating chamber 3, and the pressure in the preheating chamber 3 and the front chamber 4 is adjusted as soon as pressure adjustment is completed. It is moved so that it may install in the raising / lowering type susceptor 9 provided in this.
前室４に移動させられた密閉容器５は、一部図示している昇降式の移動手段１０によって前室４から加熱室２に移動させられる。このとき、加熱室２内は、図示しない真空ポンプで予め所定の圧力である１０-1Ｐａ以下、好ましくは１０-2Ｐａ以下の真空、更に好ましくは、１０-5Ｐａ以下の真空、又は予め圧力１０-5Ｐａ以下の高真空に到達した後に若干の不活性ガスを導入し、１０-1Ｐａ以下、好ましくは１０-2Ｐａ以下の希薄ガス雰囲気下にし、加熱ヒータ１１によって１４００℃〜２３００℃に設定されていることが好ましい。加熱室２内の状態をこのように設定しておくことで、密閉容器５を前室４から加熱室２内に移動することによって、密閉容器５を１４００℃〜２３００℃に急速に加熱することができる。また、加熱室２には、加熱ヒータ１１の周囲に反射鏡１２が配置されており、加熱ヒータ１１の熱を反射して加熱ヒータ１１の内部に位置する密閉容器５側に集中するようにしている。 The sealed container 5 moved to the front chamber 4 is moved from the front chamber 4 to the heating chamber 2 by a lifting / lowering moving means 10 partially illustrated. At this time, the heating chamber 2, following 10 -1 Pa in advance predetermined pressure by a vacuum pump (not shown), preferably 10 -2 Pa or less of vacuum, more preferably, 10 -5 Pa or less of vacuum, or After reaching a high vacuum of 10 −5 Pa or less in advance, a slight inert gas is introduced to make a rare gas atmosphere of 10 −1 Pa or less, preferably 10 −2 Pa or less. it is preferably set to 23 00 ° C.. A state in the heating chamber 2 By setting in this way, by moving in the heating chamber 2 a closed container 5 from the front compartment 4, rapidly heats the sealed container 5 to 1400 ℃ ~ 23 00 ℃ be able to. In addition, in the heating chamber 2, a reflecting mirror 12 is disposed around the heater 11 so that the heat of the heater 11 is reflected and concentrated on the side of the sealed container 5 located inside the heater 11. Yes.
また、加熱室２内の加熱ヒータ１１の内側には、密閉容器５内から漏出するＳｉ蒸気を、加熱ヒータ１１と接触しないように除去する汚染物除去機構２０が設けられている。これによって、加熱ヒータ１１がＳｉ蒸気と反応し劣化することを抑制できる。この、汚染物除去機構２０は、密閉容器５内から漏出するシリコン蒸気を除去するものであれば、特に限定されるものではない。 Further, a contaminant removal mechanism 20 for removing Si vapor leaking from the sealed container 5 so as not to come into contact with the heater 11 is provided inside the heater 11 in the heating chamber 2. Thereby, it can suppress that the heater 11 reacts with Si vapor | steam and deteriorates. The contaminant removal mechanism 20 is not particularly limited as long as it removes silicon vapor leaking from the sealed container 5.
加熱ヒータ１１は、タンタル等の金属製の抵抗加熱ヒータであり、サセプタ９に設置されているベースヒータ１１ａと、側部及び上部が一体に筒状に形成された上部ヒータ１１ｂとで構成されている。このように、密閉容器５を覆うように加熱ヒータ１１が配置されているため、密閉容器５を均等に加熱することが可能となる。なお、加熱室２の加熱方式は、本実施形態例に示す抵抗加熱ヒータに限定されるものではなく、例えば、高周波誘導加熱式であっても構わない。 The heater 11 is a resistance heater made of metal such as tantalum, and includes a base heater 11a installed on the susceptor 9 and an upper heater 11b in which a side portion and an upper portion are integrally formed in a cylindrical shape. Yes. Thus, since the heater 11 is arrange | positioned so that the airtight container 5 may be covered, it becomes possible to heat the airtight container 5 equally. Note that the heating method of the heating chamber 2 is not limited to the resistance heater shown in the present embodiment, and may be a high frequency induction heating method, for example.
密閉容器５は、図２に示すように、上容器５ａと、下容器５ｂとで構成され、それぞれタンタル又は炭化タンタルのいずれかで形成されている。そして、上容器５ａと下容器５ｂとの嵌め合わせ時の嵌合部の遊びは２ｍｍ以下であることが好ましい。これによって、密閉容器５内への不純物の混入を抑制することができる。また、遊びを２ｍｍ以下とすることによって、密閉容器５内のＳｉ分圧を１０Ｐａ以下とならないように制御することもできる。このため、密閉容器５内のＳｉＣ分圧及びＳｉ分圧を高め、単結晶ＳｉＣ基板１６及び多結晶ＳｉＣ基板１４，１５、極薄金属Ｓｉ融液１７の昇華の防止に寄与するようになる。なお、この上容器５ａと下容器５ｂとの嵌め合い時の嵌合部の遊びが２ｍｍよりも大きい場合は、密閉容器５内のＳｉ分圧を所定圧に制御することが困難になるばかりでなく、不純物がこの嵌合部を介して密閉容器５内に侵入することもあるため、好ましくない。この密閉容器５は、図２に示すように、形状が四角のものに限らず、円形のものであっても良い。 As shown in FIG. 2, the sealed container 5 includes an upper container 5a and a lower container 5b, and each is formed of either tantalum or tantalum carbide. And it is preferable that the play of the fitting part at the time of fitting with the upper container 5a and the lower container 5b is 2 mm or less. Thereby, mixing of impurities into the hermetic container 5 can be suppressed. Further, by setting the play to 2 mm or less, the Si partial pressure in the sealed container 5 can be controlled so as not to be 10 Pa or less. For this reason, the SiC partial pressure and the Si partial pressure in the sealed container 5 are increased, thereby contributing to prevention of sublimation of the single crystal SiC substrate 16, the polycrystalline SiC substrates 14 and 15, and the ultrathin metal Si melt 17. If the play of the fitting portion when the upper container 5a and the lower container 5b are fitted is larger than 2 mm, it is difficult to control the Si partial pressure in the sealed container 5 to a predetermined pressure. In addition, impurities may enter the sealed container 5 through the fitting portion, which is not preferable. As shown in FIG. 2, the sealed container 5 is not limited to a square shape but may be a circular shape.
また、下容器５ｂには、図３及び図４に示すように、３本の支持部１３が設けられている。この支持部１３によって、後述する種結晶となる多結晶ＳｉＣ基板１４を支持している。なお、支持部１３は、本実施形態例に示すようなピン状のものである必要はなく、例えば、ＳｉＣ等で形成されているリング状のものであってもよい。 Moreover, as shown in FIG.3 and FIG.4, the three support parts 13 are provided in the lower container 5b. This support portion 13 supports a polycrystalline SiC substrate 14 that becomes a seed crystal to be described later. In addition, the support part 13 does not need to be a pin-shaped thing as shown in this embodiment, For example, the ring-shaped thing formed with SiC etc. may be sufficient.
図３は上容器５ａと下容器５ｂとが嵌合した状態の密閉容器５内に設置されている種結晶となる６Ｈ型の単結晶ＳｉＣ基板１６と、この単結晶ＳｉＣ基板１６を挟み込む多結晶ＳｉＣ基板１５と、これらの間に形成される極薄金属Ｓｉ融液１７の状態を示している。なお、極薄金属Ｓｉ融液１７は熱処理時に形成されるものであり、この極薄金属Ｓｉ融液１７のＳｉ源となるのは、種結晶となる単結晶ＳｉＣ基板１６の表面に予め金属ＳｉをＣＶＤ等によって１０μｍから５０μｍとなるよう膜を形成するか、Ｓｉ粉末を置く等その方法は特に限定されない。 FIG. 3 shows a 6H-type single crystal SiC substrate 16 serving as a seed crystal installed in the sealed container 5 in a state where the upper container 5a and the lower container 5b are fitted, and a polycrystal sandwiching the single crystal SiC substrate 16 therebetween. The state of the SiC substrate 15 and the ultrathin metal Si melt 17 formed therebetween is shown. The ultrathin metal Si melt 17 is formed at the time of heat treatment, and the Si source of the ultrathin metal Si melt 17 is preliminarily formed on the surface of the single crystal SiC substrate 16 to be a seed crystal on the surface of the metal Si. The method is not particularly limited, such as forming a film to 10 μm to 50 μm by CVD or placing Si powder.
図３に示すように、これら単結晶ＳｉＣ基板１６、多結晶ＳｉＣ基板１４，１５及び極薄金属Ｓｉ融液１７は、密閉容器５を構成する下容器５ｂに設けられている支持部１３に載置されて、密閉容器５内に収納されている。ここで、単結晶ＳｉＣ基板１６は、昇華法で作製された単結晶６Ｈ−ＳｉＣのウェハーより所望の大きさ（１０×１０〜２０×２０ｍｍ）に切り出されたものである。また、多結晶ＳｉＣ基板１４，１５は、ＣＶＤ法で作製されたＳｉ半導体製造工程でダミーウェハーとして使用されるＳｉＣから所望の大きさに切り出されたものを使用することができる。これら各基板１６，１４，１５は表面が鏡面に研磨加工され、表面に付着した油類、酸化膜、金属等が洗浄等によって除去されている。ここで、下部側に位置する多結晶ＳｉＣ基板１４は単結晶ＳｉＣ基板１６の密閉容器５からの侵食を防止するもので、単結晶ＳｉＣ基板１６上に液相エピタキシャル成長する単結晶ＳｉＣの品質向上に寄与するものである。 As shown in FIG. 3, the single crystal SiC substrate 16, the polycrystalline SiC substrates 14 and 15, and the ultrathin metal Si melt 17 are placed on the support portion 13 provided in the lower container 5 b constituting the sealed container 5. Placed in a sealed container 5. Here, the single crystal SiC substrate 16 is cut out to a desired size (10 × 10 to 20 × 20 mm) from a single crystal 6H—SiC wafer manufactured by a sublimation method. Further, the polycrystalline SiC substrates 14 and 15 can be made by cutting to a desired size from SiC used as a dummy wafer in the Si semiconductor manufacturing process manufactured by the CVD method. The surface of each of the substrates 16, 14, 15 is polished into a mirror surface, and oils, oxide films, metals, etc. adhering to the surface are removed by washing or the like. Here, the polycrystalline SiC substrate 14 located on the lower side prevents erosion of the single crystal SiC substrate 16 from the sealed container 5, and improves the quality of single crystal SiC that is liquid phase epitaxially grown on the single crystal SiC substrate 16. It contributes.
また、この密閉容器５内には、熱処理時におけるＳｉＣの昇華、Ｓｉの蒸発を制御するためのＳｉ片と共に設置することもできる。Ｓｉ片を同時に設置することによって、熱処理時に昇華して密閉容器５内のＳｉＣ分圧及びＳｉ分圧を高め、単結晶ＳｉＣ基板１６及び多結晶ＳｉＣ基板１４，１５、極薄金属Ｓｉ融液１７の昇華の防止に寄与するようになる。また、密閉容器５内の圧力を加熱室２内の圧力よりも高くなるように調整でき、これによって、上容器５ａと下容器５ｂとの嵌合部から常にＳｉ蒸気を放出でき、不純物の密閉容器５内への侵入を防止できる。 Moreover, it can also install in this airtight container 5 with the Si piece for controlling the sublimation of SiC at the time of heat processing, and evaporation of Si. By simultaneously installing the Si pieces, the SiC partial pressure and the Si partial pressure in the hermetic container 5 are sublimated during the heat treatment to increase the single crystal SiC substrate 16, the polycrystalline SiC substrates 14 and 15, and the ultrathin metal Si melt 17. Contributes to the prevention of sublimation. Further, the pressure in the sealed container 5 can be adjusted to be higher than the pressure in the heating chamber 2, whereby Si vapor can always be released from the fitting portion between the upper container 5 a and the lower container 5 b, and the impurity is sealed. Intrusion into the container 5 can be prevented.
このように構成された密閉容器５は、予備加熱室３内に設置された後、１０-5Ｐａ以下に設定され、予備加熱室３に設けられているランプ及び又はロッドヒ−ター等の加熱手段６によって８００℃以上、好ましくは１０００℃以上に加熱される。この際、加熱室２内も同様に、１０-2Ｐａ以下に設定された後、１４００℃〜２３００℃に加熱しておくことが好ましい。 After the airtight container 5 configured in this way is installed in the preheating chamber 3, it is set to 10 −5 Pa or less, and heating means such as a lamp and / or a rod heater provided in the preheating chamber 3 is provided. 6 is heated to 800 ° C. or higher, preferably 1000 ° C. or higher. In this case, as well inside the heating chamber 2, after being set below 10 -2 Pa, it is preferable to heat the 1400 ℃ ~ 23 00 ℃.
予備加熱室３内で予備加熱された密閉容器５は、ゲートバルブ７を開き、前室４のサセプタ９に移動して、昇降手段１０によって、１４００℃〜２３００℃に加熱されている加熱室２内に移動される。これによって、密閉容器５は、３０分以内の短時間で急速に１４００℃〜２３００℃に加熱される。加熱室２での熱処理温度は、密閉容器５内に同時に設置している金属Ｓｉ片が溶融する温度であれば良いが、１４００℃〜２３００℃にする。処理温度を高温で行なうほど、溶融ＳｉとＳｉＣとの濡れ性が上昇し、溶融Ｓｉが毛細管現象によって、単結晶ＳｉＣ基板１６と多結晶ＳｉＣ基板１４，１５との間に浸透しやすくなる。これによって、単結晶ＳｉＣ基板１６と多結晶ＳｉＣ基板１４，１５との間に厚み５０μｍ以下の極薄金属Ｓｉ融液１７を介在させることができる。 Closed container 5, which is preheated in the preheating chamber 3, the gate valve 7, by moving the susceptor 9 of the front chamber 4, by the lifting means 10, the heating chamber which is heated to 1400 ℃ ~ 23 00 ℃ 2 is moved. Thus, the closed container 5 is heated rapidly to 1400 ℃ ~ 23 00 ℃ in a short time within 30 minutes. The heat treatment temperature in the heating chamber 2, the metal Si pieces are installed at the same time in the closed container 5 may be a temperature which melts, to 1400 ℃ ~ 23 00 ℃. As the processing temperature is increased, the wettability between molten Si and SiC increases, and the molten Si easily penetrates between the single crystal SiC substrate 16 and the polycrystalline SiC substrates 14 and 15 by capillary action. Thereby, an ultrathin metal Si melt 17 having a thickness of 50 μm or less can be interposed between the single crystal SiC substrate 16 and the polycrystalline SiC substrates 14 and 15.
また、この際に、できるだけ、短時間で１４００℃〜２３００℃とすることによって、結晶成長を短時間で終了することが可能となり結晶成長の効率化が可能となる。 Further, in this case, as far as possible, by a short time 1400 ℃ ~ 23 00 ℃, it is possible to terminate in a short time crystal growth is possible to streamline the crystal growth.
また、熱処理時間は、生成される単結晶ＳｉＣが所望の厚みとなるように適宜選択することが可能である。ここで、Ｓｉ源となる金属Ｓｉは、量が多くなると、熱処理時に溶融する量が多くなり、極薄金属Ｓｉ融液が５０μｍ以上の厚みになると、金属Ｓｉ融液が不安定になり、またＣの輸送が阻害され、本発明に係る単結晶ＳｉＣの育成に適さず、また単結晶ＳｉＣの形成に必要でないＳｉが、溶融し密閉容器５の底部に溜まり、単結晶ＳｉＣ形成後に再度固化した金属Ｓｉを除去する必要が生じる。このため、金属Ｓｉの大きさ及び厚さについては、形成する単結晶ＳｉＣの大きさに合わせ適宜選択する。 Further, the heat treatment time can be appropriately selected so that the single crystal SiC to be produced has a desired thickness. Here, when the amount of the metal Si serving as the Si source increases, the amount melted during the heat treatment increases, and when the ultrathin metal Si melt has a thickness of 50 μm or more, the metal Si melt becomes unstable. The transport of C is hindered, and is not suitable for growing single crystal SiC according to the present invention, and Si that is not necessary for the formation of single crystal SiC melts and accumulates at the bottom of the hermetic vessel 5, and solidifies again after the single crystal SiC is formed. Metal Si needs to be removed. For this reason, the size and thickness of the metal Si are appropriately selected according to the size of the single crystal SiC to be formed.
ところで、単結晶ＳｉＣの成長メカニズムについて簡単に説明すると、熱処理に伴い単結晶ＳｉＣ基板１６と上部の多結晶ＳｉＣ基板１５との間に溶融したＳｉが侵入して、両基板１６，１５の界面に厚さ約３０μｍ〜５０μｍの金属Ｓｉ融液層１７を形成する。この金属Ｓｉ融液層１７は、熱処理温度が高温になるにしたがって、薄くなり、３０μｍ程度となる。そして、多結晶ＳｉＣ基板２から流れ出したＣ原子はＳｉ融液層を通して単結晶ＳｉＣ基板１６に供給され、この単結晶ＳｉＣ基板１上に６Ｈ−ＳｉＣ単結晶として液相エピタキシャル成長（以下、ＬＰＥという。）する。このように、種結晶となる単結晶ＳｉＣ基板１６と多結晶ＳｉＣ基板１４との間が小さいため、熱処理時に熱対流が生成しない。このため、形成される単結晶ＳｉＣと、種結晶となる単結晶ＳｉＣ基板１６と界面が非常に滑らかとなり、この界面に歪み等が形成されない。したがって、非常に平滑な単結晶ＳｉＣが形成される。また、熱処理時にＳｉＣの核生成が抑制されるため、形成される単結晶ＳｉＣの微小結晶粒界の生成を抑制することができる。本実施形態に係る単結晶ＳｉＣの育成方法においては、溶融したＳｉが単結晶ＳｉＣ基板１６と多結晶ＳｉＣ基板１５との間にのみ侵入することから、他の不純物が成長する単結晶ＳｉＣ中に侵入することがないため、バッググランド５×１０15／ｃｍ3以下の高純度の単結晶ＳｉＣを生成することが可能となる。 By the way, the growth mechanism of single crystal SiC will be briefly described. As a result of the heat treatment, molten Si enters between the single crystal SiC substrate 16 and the upper polycrystalline SiC substrate 15 and enters the interface between the substrates 16 and 15. A metal Si melt layer 17 having a thickness of about 30 μm to 50 μm is formed. The metal Si melt layer 17 becomes thinner as the heat treatment temperature becomes higher, and becomes about 30 μm. The C atoms flowing out of the polycrystalline SiC substrate 2 are supplied to the single crystal SiC substrate 16 through the Si melt layer, and liquid phase epitaxial growth (hereinafter referred to as LPE) as 6H—SiC single crystal on the single crystal SiC substrate 1. ) Thus, since the space between the single-crystal SiC substrate 16 serving as the seed crystal and the polycrystalline SiC substrate 14 is small, thermal convection is not generated during the heat treatment. Therefore, the interface between the formed single crystal SiC and the single crystal SiC substrate 16 serving as a seed crystal becomes very smooth, and no distortion or the like is formed at the interface. Therefore, very smooth single crystal SiC is formed. Moreover, since the nucleation of SiC is suppressed during the heat treatment, the generation of the fine crystal grain boundaries of the formed single crystal SiC can be suppressed. In the method for growing single crystal SiC according to the present embodiment, melted Si enters only between the single crystal SiC substrate 16 and the polycrystalline SiC substrate 15, and therefore, in the single crystal SiC where other impurities grow. Since it does not enter, high-purity single crystal SiC having a background of 5 × 10 15 / cm 3 or less can be produced.
図５は、前述の方法によって成長した単結晶ＳｉＣの表面状態を示す顕微鏡写真を示す図である。図５において、（ａ）は表面モフォロジー、（ｂ）はその断面を示すものである。図５に示すように、ＬＰＥ法による結晶の成長表面は、非常に平坦なテラスとステップ構造が観察できる。 FIG. 5 is a view showing a micrograph showing the surface state of single crystal SiC grown by the above-described method. In FIG. 5, (a) shows the surface morphology, and (b) shows the cross section. As shown in FIG. 5, a very flat terrace and step structure can be observed on the growth surface of the crystal by the LPE method.
図６は、この表面を原子間力顕微鏡（以下、ＡＦＭという。）によって観察した結果を示す図である。図６から観察できるように、ステップの高さはそれぞれ４．０ｎｍ、８．４ｎｍであることがわかる。これは、ＳｉＣ分子（ＳｉＣ１分子層の高さは０．２５ｎｍ）の３分子層を基本とした整数倍の高さである。このように、非常に平坦な表面となっていることがわかる。 FIG. 6 is a diagram showing the results of observing this surface with an atomic force microscope (hereinafter referred to as AFM). As can be observed from FIG. 6, the step heights are 4.0 nm and 8.4 nm, respectively. This is an integer multiple height based on a trimolecular layer of SiC molecules (SiC 1 molecular layer has a height of 0.25 nm). Thus, it can be seen that the surface is very flat.
また、図５の表面形態の顕微鏡写真からもわかるように、表面にマイクロパイプ欠陥が観察されない。これらのことから、本発明による単結晶ＳｉＣは、表面に形成されるマイクロパイプ欠陥の密度が１／ｃｍ2以下と非常に少なくなり、表面に形成されるテラスの幅も１０μｍ以上と広く、平坦で欠陥の少ないものであることがわかる。 Further, as can be seen from the micrograph of the surface form of FIG. 5, no micropipe defects are observed on the surface. Therefore, the single crystal SiC according to the present invention has a very small density of micropipe defects formed on the surface of 1 / cm 2 or less, and the width of the terrace formed on the surface is as wide as 10 μm or more and is flat. It turns out that it is a thing with few defects.
一般に、結晶のエピタキシャル成長は、１分子層ごとに行なわれる。ところが、本実施形態に係る単結晶ＳｉＣでは、表面に１０μｍ以上の幅広のテラスと３分子層を最小単位とした高さのステップで構成されている。このことから、結晶成長の過程で、ステップバンチングが起きたと考えられる。このステップバンチング機構は、結晶成長中の表面自由エネルギーの効果によって説明することができる。本実施形態例に係る単結晶６Ｈ−ＳｉＣは、単位積層周期の中にＡＢＣと、ＡＣＢという２種類の積層周期の方向がある。そこで、積層方向の折れ曲がる層から番号を１、２、３と付けることにより、図７に示すように３種類の表面が規定できる。そして、各面のエネルギーは以下のように求められている（Ｔ．Ｋｉｍｏｔｏ， ｅｔ ａｌ．，Ｊ．Ａｐｐｌ．Ｐｈｙｓ．８１（１９９７）３４９４−３５００）。
６Ｈ１＝１．３３ｍｅＶ
６Ｈ２＝６．５６ｍｅＶ
６Ｈ３＝２．３４ｍｅＶ
この様に面によってエネルギーが異なるため、テラスの広がる速度が異なる。すなわち、テラスは、各面の表面自由エネルギーの高いものほど成長速度が速く、図７（ａ）（ｂ）（ｃ）に示すように、３周期おきにステップハンチングが起きる。また、本実施形態例では、積層周期の違い（ＡＢＣ又はＡＣＢ）により、ステップ面からでている未結合手の数が１段おきに異なり、このステップ端から出ている未結合手の数の違いにより、３分子単位でさらにステップバンチングが起きると考えられる。１ステップの前進速度は、ステップから出ている未結合手が１本の所では遅く、２本の所では速いと考えられる。この様にして、６Ｈ−ＳｉＣでは格子定数の半整数倍の高さ単位でステップバンチングが進み、成長後、単結晶ＳｉＣの表面は３分子層を最小単位とした高さのステップと、平坦なテラスとで覆われると考えられる。
In general, the epitaxial growth of crystals is performed for each molecular layer. However, the single crystal SiC according to the present embodiment is configured with a step having a height of 10 μm or more on a surface and a trimolecular layer as a minimum unit. This suggests that step bunching occurred during the crystal growth process. This step bunching mechanism can be explained by the effect of surface free energy during crystal growth. The single crystal 6H-SiC according to the present embodiment has two types of stacking cycle directions, ABC and ACB, in the unit stacking cycle. Therefore, by assigning numbers 1, 2, and 3 from the folding layers in the stacking direction, three types of surfaces can be defined as shown in FIG. And the energy of each surface is calculated | required as follows (T.Kimoto, et al., J.Appl.Phys.81 (1997) 3494-3500).
6H1 = 1.33 meV
6H2 = 6.56 meV
6H3 = 2.34 meV
Since the energy varies depending on the surface in this way, the spreading speed of the terrace varies. That is, the terrace has a higher growth rate as the surface free energy of each surface is higher, and step hunting occurs every three periods as shown in FIGS. 7 (a), 7 (b), and 7 (c). In this embodiment, the number of unbonded hands coming out of the step surface differs every other stage due to the difference in stacking cycle (ABC or ACB). Due to the difference, it is considered that further step bunching occurs in units of 3 molecules. The forward speed of one step is considered to be slow when the number of unbonded hands coming out of the step is one, and fast at two places. In this way, in 6H-SiC, step bunching proceeds in units of half integer multiples of the lattice constant, and after growth, the surface of the single crystal SiC is flat with a step having a height of three molecular layers as a minimum unit. It is thought to be covered with a terrace.
なお、以上説明したように、本発明に係る単結晶ＳｉＣは、ステップバンチングによってそのテラスが形成されている。そのため、ステップは、単結晶ＳｉＣの端部付近に集中して形成されるようになる。前述した図５及び図６は、ステップ部分を観察するために単結晶ＳｉＣの端部部分を観察したものである。 As described above, the single crystal SiC according to the present invention has its terrace formed by step bunching. Therefore, the steps are formed in a concentrated manner near the end portion of the single crystal SiC. 5 and 6 described above are obtained by observing the end portion of the single crystal SiC in order to observe the step portion.
また、本実施形態例における単結晶ＳｉＣは、その成長温度が１４００℃〜２３００℃と従来の単結晶ＳｉＣの液相成長温度に比べて非常に高く、また、短時間で１４００℃〜２３００℃に加熱出来る。成長温度が上がると、種結晶となる単結晶ＳｉＣと多結晶ＳｉＣとの間に形成されるＳｉ融液中へのＣの溶解濃度が増加する。また温度の上昇とともにＳｉ融液中でのＣの拡散が大きくなると考えられる。このように、Ｃの供給源と種結晶とが非常に近接しているため、５００μｍ／ｈｒという速い成長速度とする事も条件次第で可能になる。 The single crystal SiC in this embodiment, the growth temperature is very high as compared with the liquid phase growth temperature of 1400 ℃ ~ 23 00 ℃ and conventional single crystal SiC, also briefly at 1400 ° C. ~ 23 00 Can be heated to ℃. As the growth temperature rises, the dissolution concentration of C in the Si melt formed between the single crystal SiC that becomes the seed crystal and the polycrystalline SiC increases. Further, it is considered that the diffusion of C in the Si melt increases as the temperature rises. Thus, since the C supply source and the seed crystal are very close to each other, a high growth rate of 500 μm / hr can be achieved depending on conditions.
このように、本実施形態例に係る単結晶ＳｉＣは、表面のマイクロパイプ欠陥の密度が１／ｃｍ2以下であり、１０μｍ以上の幅広のテラスが形成されることから、単結晶ＳｉＣ形成後に、機械加工等の表面処理が不要となる。また、結晶欠陥等が少ないために、発光ダイオードや、各種半導体ダイオードとして使用することが可能となる。加えて、結晶の成長が温度に依存せず、種結晶及びＣの供給源の結晶の表面エネルギーに依存することから、処理炉内の厳密な温度制御の必要性がなくなることから、製造コストの大幅な低減化が可能となる。さらに、種結晶となる単結晶ＳｉＣ及びＣの供給源である多結晶ＳｉＣとの間隔が非常に小さことから、熱処理時の熱対流を抑制することができる。また種結晶となる単結晶ＳｉＣ及びＣの供給源である多結晶ＳｉＣとの間に温度差が形成されにくいことから、熱平衡状態で熱処理することができる。 Thus, the single crystal SiC according to the present embodiment example has a density of micropipe defects on the surface of 1 / cm 2 or less and a wide terrace of 10 μm or more is formed. No surface treatment such as machining is required. Moreover, since there are few crystal defects etc., it can be used as a light emitting diode or various semiconductor diodes. In addition, since the crystal growth does not depend on the temperature and depends on the surface energy of the seed crystal and the crystal of the source of C, the need for strict temperature control in the processing furnace is eliminated, thereby reducing the manufacturing cost. Significant reduction is possible. Furthermore, since the distance between the single crystal SiC as the seed crystal and the polycrystalline SiC that is the supply source of C is very small, thermal convection during heat treatment can be suppressed. In addition, since a temperature difference is unlikely to be formed between single crystal SiC as a seed crystal and polycrystalline SiC which is a supply source of C, heat treatment can be performed in a thermal equilibrium state.
なお、本実施形態例では、種結晶として、６Ｈ−ＳｉＣを用いたが、４Ｈ−ＳｉＣを使
用することも可能である。
In this embodiment, 6H—SiC is used as a seed crystal, but 4H—SiC can also be used.
なお、本実施形態例では、種結晶として、（０００１）Ｓｉを用いたが、（１１−２０）などのその他の面方位のものを使用することも可能である。 In this embodiment, (0001) Si is used as the seed crystal, but other surface orientations such as (11-20) can also be used.
また、本発明に係る単結晶ＳｉＣは、種結晶となる単結晶ＳｉＣ及びＣの供給源となる多結晶ＳｉＣ基板の大きさを適宜選択することによって形成される単結晶ＳｉＣの大きさを制御することができる。また、形成される単結晶ＳｉＣと種結晶との間に歪みが形成されることもないため、非常に平滑な表面の単結晶ＳｉＣとできることから、表面の改質膜として適用することも可能である。 In addition, the single crystal SiC according to the present invention controls the size of the single crystal SiC formed by appropriately selecting the size of the single crystal SiC serving as the seed crystal and the size of the polycrystalline SiC substrate serving as the supply source of C. be able to. In addition, since no distortion is formed between the single crystal SiC to be formed and the seed crystal, single crystal SiC with a very smooth surface can be obtained, so that it can be applied as a surface modification film. is there.
さらに、種結晶となる単結晶ＳｉＣとＣの供給源である多結晶ＳｉＣを交互に積層、または横に並べて前述の方法によって、熱処理することによって、同時に多量の単結晶ＳｉＣを製造することも可能である。 Furthermore, it is also possible to produce a large amount of single crystal SiC at the same time by alternately laminating single crystal SiC as a seed crystal and polycrystalline SiC, which is a supply source of C, or arranging them side by side and heat-treating them by the method described above. It is.
また本発明に係る単結晶ＳｉＣの製造方法では、多結晶ＳｉＣ基板及び金属Ｓｉ中にあらかじめＡｌまたはＢ等のＩＩＩ族金属の不純物を添加しておくか、さらには成長中の雰囲気中に窒素、ＡｌまたはＢ等のＳｉＣの伝導型を制御する元素を含むガスを送り込むことにより、成長結晶のｐ型、ｎ型の伝導型を任意に制御することが可能である。 Further, in the method for producing single-crystal SiC according to the present invention, impurities of a group III metal such as Al or B are added to the polycrystalline SiC substrate and the metal Si in advance, or further, nitrogen, By feeding a gas containing an element that controls the conductivity type of SiC such as Al or B, it is possible to arbitrarily control the p-type and n-type conductivity types of the grown crystal.
１ 熱処理炉
２ 加熱室
３ 予備加熱室
４ 前室
５ 密閉容器
５ａ 上容器
５ｂ 下容器
６ 加熱手段
７ ゲートバルブ
８ テーブル
９ サセプタ
１０ 移動手段
１１ 加熱ヒータ
１２ 反射鏡
DESCRIPTION OF SYMBOLS 1 Heat processing furnace 2 Heating chamber 3 Preheating chamber 4 Front chamber 5 Sealed container 5a Upper container 5b Lower container 6 Heating means 7 Gate valve 8 Table 9 Susceptor 10 Moving means 11 Heating heater 12 Reflective mirror
Claims (6)
前記単結晶炭化ケイ素基板と多結晶炭化ケイ素基板との間で温度差を設けずに、前記単結晶炭化ケイ素基板と多結晶炭化ケイ素基板とを１４００℃〜２３００℃に加熱して微結晶粒界の存在しない、表面のマイクロパイプ欠陥密度が１／ｃｍ2以下である単結晶炭化ケイ素を製造する単結晶炭化ケイ素の液相エピタキシャル成長法。 A single crystal silicon carbide substrate to be a seed crystal and a polycrystalline silicon carbide substrate are stacked, placed in a sealed container, and subjected to high-temperature heat treatment, so that the single crystal silicon carbide substrate and the polycrystalline silicon carbide substrate are placed between each other. In addition, a liquid crystal epitaxial growth method of single crystal silicon carbide in which an ultrathin metal silicon melt is interposed during the heat treatment, and single crystal silicon carbide is liquid phase epitaxially grown on the single crystal silicon carbide substrate,
Said without providing a temperature difference between the single crystal silicon carbide substrate and the polycrystalline silicon carbide substrate, wherein the heating the monocrystalline silicon carbide substrate and the polycrystalline silicon carbide substrate 1 400 ° C. to 2300 ° C. microcrystal grains A liquid-phase epitaxial growth method of single-crystal silicon carbide for producing single-crystal silicon carbide having a surface with a micropipe defect density of 1 / cm 2 or less.
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| JP5224256B2 (en) * | 2005-06-02 | 2013-07-03 | 学校法人関西学院 | Single crystal silicon carbide substrate processing method, semiconductor device manufacturing method |
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| US9797064B2 (en) | 2013-02-05 | 2017-10-24 | Dow Corning Corporation | Method for growing a SiC crystal by vapor deposition onto a seed crystal provided on a support shelf which permits thermal expansion |
| US8940614B2 (en) | 2013-03-15 | 2015-01-27 | Dow Corning Corporation | SiC substrate with SiC epitaxial film |
| JP5688780B2 (en) * | 2013-05-07 | 2015-03-25 | 学校法人関西学院 | SiC substrate, carbon supply feed substrate, and SiC substrate with carbon nanomaterial |
| US9279192B2 (en) | 2014-07-29 | 2016-03-08 | Dow Corning Corporation | Method for manufacturing SiC wafer fit for integration with power device manufacturing technology |
| WO2021060365A1 (en) * | 2019-09-27 | 2021-04-01 | 学校法人関西学院 | Method for producing semiconductor substrates and device for producing semiconductor substrates |
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| JPH07300666A (en) * | 1994-04-27 | 1995-11-14 | Nissin Electric Co Ltd | Production of molecular beam source for silicon evaporation and crucible used for the same |
| JP4110601B2 (en) * | 1998-01-13 | 2008-07-02 | 昭和電工株式会社 | Method for producing silicon carbide single crystal |
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| JP2000053500A (en) * | 1998-08-06 | 2000-02-22 | Nippon Pillar Packing Co Ltd | METHOD AND DEVICE FOR GROWING SINGLE CRYSTAL SiC |
| JP2000302599A (en) * | 1999-04-23 | 2000-10-31 | New Japan Radio Co Ltd | Epitaxial growth method of silicon carbide |
| JP2002047100A (en) * | 2000-07-31 | 2002-02-12 | Nippon Pillar Packing Co Ltd | METHOD FOR GROWING SINGLE CRYSTAL SiC |
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